docs: def _compute_normalization(self, normalize):
          """
          Helper function that computes (corrected) normalization factor
          of the original image data. This quantity is computed as the
          inverse "raw image norm" (or total "flux" of model's image)
          corrected by the ``normalization_correction``:
  
          .. math::
              N = 1/(\\Phi * C),
  
          where :math:`\\Phi` is the "total flux" of model's image as
          computed by `_compute_raw_image_norm` and *C* is the
          normalization correction factor. :math:`\\Phi` is computed only
          once if it has not been previously computed. Otherwise, the
          existing (stored) value of :math:`\\Phi` is not modified as
          :py:class:`FittableImageModel` does not allow image data to be
          modified after the object is created.
  
          .. note::
              Normally, this function should not be called by the
              end-user. It is intended to be overriden in a subclass if
              one desires to change the way the normalization factor is
              computed.
          """
  
          self._normalization_constant = 1.0 / self._normalization_correction
  
          if normalize:
              # compute normalization constant so that
              # N*C*sum(data) = 1:
              if self._img_norm is None:
                  self._img_norm = self._compute_raw_image_norm(self._data)
  
              if self._img_norm != 0.0 and np.isfinite(self._img_norm):
                  self._normalization_constant /= self._img_norm
                  self._normalization_status = 0
  
              else:
                  self._normalization_constant = 1.0
                  self._normalization_status = 1
                  warnings.warn("Overflow encountered while computing "
                                "normalization constant. Normalization "
                                "constant will be set to 1.", NonNormalizable)
  
          else:
              self._normalization_status = 2